Antonio Tarver is adamant Joe Calzaghe will have to do more than beat Bernard Hopkins to become a true two-weight great.

Calzaghe moves up a division in Las Vegas on April 19 to clash with ex-middleweight supremo Hopkins - holder of the Ring belt after the magazine nominated him the world's best light-heavyweight in the wake of his 2006 win over Tarver.

But brash 39-year-old American Tarver insists the true champion will emerge a week earlier in Tampa, Florida, when he challenges Sheffield's IBF world title holder Clinton Woods and WBC champion Chad Dawson defends against former world title-holder Glen Johnson.

The plan is for a showdown between the two winners to find the top man at 175lb.

"We're not going to speak of Calzaghe," said Tarver - in London for a heated verbal spar with Woods - before doing just that. "He's a great super-middleweight champion but when he comes up to light-heavy he'll be in uncharted waters."

Tarver tried to dismiss his own defeat at the hands of Hopkins by saying: "On my worst day, he couldn't put me out."

He fancies the Welshman to beat 43-year-old Hopkins, adding: "I like Calzaghe in that fight because he's quick enough to get the job done against the old man."

But Tarver added: "Hopkins is crafty enough to make a good fighter look bad."